引言:最近在看一个开源的聊天室AjaxChat 时看到一个被引用的包:javawebparts,处于好奇去看了一下,突然发现这么好的一个常用web组件不去用实在是太可惜了,下面逐一介绍,详细文档大家可以去官方文档看看,最好看它的Demo,很直观。 javawebparts的口号是:不用重新发明轮子 ! 对这点我是严重支持啊,在我的身边看到N多所谓的牛人来到项目组作的第一件事就是把以前的项目推倒,重新实现自己的所谓一套先进的东西,靠,你有多先进啊,你的自己"方言"一边自我欣赏,一边还让别人接受,再来一个人又把这个推倒,循环。。。。无语. 所以,用开源吧 ,是不是绕的太远了? :) 让我们言归正传吧. 一。管理你的web配置文件信息 web的配置文件是我们经常要用到的,配置信息我们可以分为两大类,一类是最简单的"平板"型的,比如: For an XML config file like this: < config >
< firstName > Frank </ firstName > </ config > The following bean could be used: public class MyConfigBean {
在应用中你不用去自己解析xml了,javawebparts已经帮你做好了,你只要getFirstName()就可以了,是不是很方便?
private static String firstName; public void setFirstName(String inFirstName) { firstName = inFirstName; } public String getFirstName() { return firstName; } } 你所要做的工作就是在web.xml中引用一个listener,配置如下:
<context-param>
<param-name>configFile</param-name> <param-value>/WEB-INF/app_config.xml< /param-value></context-param> <context-param> <param-name>rootElement</param-name> <param-value>config</param-value> </context-param> <context-param> <param-name>configClass</param-name> <param-value>javawebparts.sampleapp. SampleAppConfigBean</param-value> </context-param> <context-param> <param-name>AjaxPartsTaglibConfig</param-name> <param-value>/WEB-INF/ajax_config.xml</param-value> </context-param> <listener> <listener-class>javawebparts.listener. AppConfigContextListener</listener-class> </listener> 这种平板型结构的数据这样就已经OK了,还有一种是复杂一点的,有层次结构,比如在Bean中可能还有collection,需要自己实现一下,也不复杂直接调用apache的Digester就可以了(实际上在javawebparts到处都有Digester的影子),需要了解的请参看 用Digester解析xml到bean 二。缓存页面 比如,我想缓存所有的gif图片,但是jpg的不缓存,web.xml中配置如下:
<filter>
<filter-name>CacheControlFilter</filter-name> <filter-class>javawebparts.filter. CacheControlFilter</filter-class> <init-param> <param-name>pathSpec</param-name> <param-value>include</param-value> </init-param> <init-param> <param-name>pathList</param-name> <param-value>*/header1.gif, *.jpg</param-value> </init-param> </filter> <filter-mapping> <filter-name>CacheControlFilter</filter-name> <url-pattern>/*</url-pattern> </filter-mapping> 它的后台实现机制很简单,内部部分代码如下:
((HttpServletResponse)response).setHeader("Pragma", "No-cache");
((HttpServletResponse)response).setHeader("Cache-Control", "no-cache,no-store,max-age=0"); ((HttpServletResponse)response).setDateHeader("Expires", 1); 三。图片压缩
<filter>
<filter-name>CompressionFilter</filter-name> <filter-class>javawebparts.filter. CompressionFilter</filter-class> <init-param> <param-name>pathSpec</param-name> <param-value>include</param-value> </init-param> <init-param> <param-name>pathList</param-name> <param-value>*/bigimage2.gif</ param-value> </init-param> <init-param> <param-name>compressType</param-name> <param-value>gzip_first</param-value> </init-param> </filter> <filter-mapping> <filter-name>CompressionFilter</filter-name> <url-pattern>/*</url-pattern> </filter-mapping> 上面的配置表示只对bigimage2.gif的文件进行压缩,其他不用,pathSpec的属性有两种include,exclude,意思已经很明确了,相反地意思,而pathList得内部实现也是用正则表达式实现的,支持*等用法.这些内部实现你觉得复杂的话就不用管它了,反正人家已经给你实现好了,你只要说"给我压缩‘美女与野兽.JPG‘"就可以了 四.控制只在设定的时间范围内访问应用 比如说只允许在工作时间内可以访问应用,其他时间禁止访问,虽然不是很普遍不过这种需求还是有的,如果自己实现还是比较麻烦的,我们用现成的,配置如下:(怎么都是配置阿?对,全部是配置就可以了,难道不好吗?太爽了啊,乖乖龙地动)
<filter>
<filter-name>AppAvailabilityFilter</filter-name> <filter-class>javawebparts.filter. AppAvailabilityFilter</filter-class> <init-param> <param-name>pathSpec</param-name> <param-value>include</param-value> </init-param> <init-param> <param-name>pathList</param-name> <param-value>*/AAFTestTarget.jsp </param-value> </init-param> <init-param> <param-name>monday</param-name> <param-value>0600-2359</param-value> </init-param> <init-param> <param-name>tuesday</param-name> <param-value>0600-2359</param-value> </init-param> <init-param> <param-name>wednesday</param-name> <param-value>0600-2359</param-value> </init-param> <init-param> <param-name>thursday</param-name> <param-value>0600-2359</param-value> </init-param> <init-param> <param-name>friday</param-name> <param-value>0600-2359</param-value> </init-param> <init-param> <param-name>saturday</param-name> <param-value>0600-2359</param-value> </init-param> <init-param> <param-name>sunday</param-name> <param-value>0600-2359</param-value> </init-param> <init-param> <param-name>redirectTo</param-name> <param-value>AAFReject.jsp< /param-value> </init-param> <init-param> <param-name>bypassCheckClass< /param-name> <param-value>javawebparts.sampleapp. AAFBypassCheck</param-value> </init-param> </filter> <filter-mapping> <filter-name>AppAvailabilityFilter</filter-name> <url-pattern>/*</url-pattern> </filter-mapping> 上面的配置很明确了吧,表示在访问AAFTestTarget.jsp 文件的时候必须在设定的时间内,其他则无限制,很清楚了哦. 五。统一重定向 redirect或者forward大家都再熟悉不过了,不过这个是基于配置的,不用你写代码,比如,你希望在访问某个目录的时候自动重订向到其他文件,或者直接转到其他网站比如google.com,配置如下:
<filter>
<filter-name>URLRedirectFilter</filter-name> <filter-class>javawebparts.filter.URLRedirectFilter</ filter-class> <init-param> <param-name>configFile</param-name> <param-value>/WEB-INF/redirect_config.xml </param-value> </filter> <filter-mapping> <filter-name>URLRedirectFilter</filter-name> <url-pattern>/*</url-pattern> </filter-mapping> 其中redirect_config.xml配置如下:
<config>
<redirect from="*/app/redirect_test/*" to="http://www.google.com" /> <forward from="*/app/forward/test.htm" to="/index.jsp" /> </config> 很直观吧?凡是访问/app/redirect_test下的所有应用都重订向到google,太简单了,我就不多说了. 六.估算每个请求所花费的时间 这个对性能调整是很有好处的,性能的调整的前提是你了解你的系统的瓶颈在什么地方,更具体的说是你的应用哪些地方花费的资源较多,一个是监控sql的执行情况,这里推荐jdbmonitor,大家可以去看看,另一种就是本文所说的查看每个请求的执行时间,他会告诉你本请求花费了多少秒,很直观了. 配置如下:
<filter>
<filter-name>ElapsedTimeFilter</filter-name> <filter-class>javawebparts.filter.ElapsedTimeFilter</ filter-class> <init-param> <param-name>pathSpec</param-name> <param-value>include</param-value> </init-param> <init-param> <param-name>pathList</param-name> <param-value>*</param-value> </init-param> </filter> <filter-mapping> <filter-name>ElapsedTimeFilter</filter-name> <url-pattern>/*</url-pattern> </filter-mapping> 上面的一个include ,一个pathList的*就代表了所有的应用都过滤,反之,你想暂时取消这个功能就直接把include换成exclude就行了 应用在启动后你直接观察后台日志就可以了,就这么就OK了,还要你做什么呢? 没有. 七.监控session的会话 经常碰到这样的一个情况,用户在登陆系统一段时间后session实效,但是他接着点击里面的连接,结果报异常,因为session里已经取不到数据了,常常是空指针错误,在每一个页面里都进行这种低级问题的判断是很烦人的,现在我们有新的方式可以一次性解决所有的问题,还是一段简单的配置:
<filter>
<filter-name>SessionInactivityFilter< /filter-name> <filter-class>javawebparts.filter. SessionInactivityFilter</filter-class> <init-param> <param-name>forwardTo</param-name> <param-value>/login.jsp< /param-value> </init-param> </filter> <filter-mapping> <filter-name>SessionInactivityFilter< /filter-name> <url-pattern>/*</url-pattern> </filter-mapping> 表示会话失效后直接重定向到登陆界面,让用户重新登陆. 八.控制访问应用的IP 出于安全考虑,过滤某些IP能或不能访问,配置如下:
<filter>
<filter-name>IPAccessControlFilter</filter-name> <filter-class>javawebparts.filter. IPAccessControlFilter</filter-class> <init-param> <param-name>pathSpec</param-name> <param-value>include</param-value> </init-param> <init-param> <param-name>pathList</param-name> <param-value>*/IACTestTarget.jsp</ param-value> </init-param> <init-param> <param-name>addressSpec</param-name> <param-value>include</param-value> </init-param> <init-param> <param-name>addressList</param-name> <param-value>localhost</param-value> </init-param> <init-param> <param-name>forwardTo</param-name> <param-value>/IACReject.jsp</param-value> </init-param> </filter> <filter-mapping> <filter-name>IPAccessControlFilter</filter-name> <url-pattern>/*</url-pattern> </filter-mapping> 以上的配置效果就是只允许是从服务器上访问应用的来源(太苛刻了吧? :)) 九.随机显示文字 比如每日一语,随机广告,很实用的,配置如下: <servlet>
<servlet-name>TextReturnerServlet</servlet-name> <servlet-class>javawebparts.servlet. TextReturnerServlet</servlet-class> <init-param> <param-name>order</param-name> <param-value>random</param-value> </init-param> <init-param> <param-name>itemsFile</param-name> <param-value>/WEB-INF/text_returner_items.xml </param-value> </init-param> </servlet> <servlet-mapping> <servlet-name>TextReturnerServlet</servlet-name> <url-pattern>/textReturner</url-pattern> </servlet-mapping> 上面的配置表示随机显示text_returner_items.xml 中的文字,text_returner_items.xml 内容如下:
<TextReturnerServletItems>
<item>0 - It‘s always darkest before the dawn</item> <item>1 - A journey of a thousand miles begins with a single step</item> <item>2 - The universe is like stupidity: both are infinite and actually, I‘m not sure about the universe</item> <item>3 - I believe there is intelligent life in the universe, except for some parts of New Jersey</item> <item>4 - If your falling of a cliff, you might as well try and fly</item> <item>5 - The cost of life is to chance the consequence</item> </TextReturnerServletItems> 十.随机显示图片 和上面有点类似,只是显示的内容可以是图片 <servlet>
<servlet-name>RedirectReturnerServlet</servlet-name> <servlet-class>javawebparts.servlet. RedirectReturnerServlet</servlet-class> <init-param> <param-name>order</param-name> <param-value>random</param-value> </init-param> <init-param> <param-name>itemsFile</param-name> <param-value> /WEB-INF/redirect_returner_items.xml</param-value> </init-param> </servlet> <servlet-mapping> <servlet-name>RedirectReturnerServlet</servlet-name> <url-pattern>/redirectReturner</url-pattern> </servlet-mapping> redirect_returner_items.xml的内容如下: <RedirectReturnerServletItems> <item>http://www.google.com/intl/en/images/logo.gif</item> <item>/img/header1.gif</item> <item>/img/mouse.gif</item> <item>http://javawebparts./logo.jpg</item> </RedirectReturnerServletItems> 我就不用解释了吧 十一.生成文字图片 你提供文字,系统帮你生成对应的图片,是不是很有用? 比如验证码里经常需要用到,生成的效果如下: 配置如下:
<servlet>
<servlet-name>TextRendererServlet</servlet-name> <servlet-class>javawebparts.servlet. TextRendererServlet</servlet-class> <init-param> <param-name>fontName</param-name> <param-value>arial</param-value> </init-param> <init-param> <param-name>fontPoint</param-name> <param-value>24</param-value> </init-param> <init-param> <param-name>color</param-name> <param-value>255,0,0 </param-value> </init-param> <init-param> <param-name>backColor</param-name> <param-value>255,255,0 </param-value> </init-param> <init-param> <param-name>stylePlain</param-name> <param-value>false</param-value> </init-param> <init-param> <param-name>styleBold</param-name> <param-value>true</param-value> </init-param> <init-param> <param-name>styleItalic</param-name> <param-value>true</param-value> </init-param> </servlet> <servlet-mapping> <servlet-name>TextRendererServlet</servlet-name> <url-pattern>/textRenderer</url-pattern> </servlet-mapping> |
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